UI: allow memory setting in flex compute offering in GiB with unit selector (#14082)

[saurabhkushwaha438]

Description

Fixes #14082

1. Conversion from MiB to GiB (Display & Rounding)

• Binary conversion is used (1 GiB = 1024 MiB).
• When offerings with predefined constraints or initial values are loaded in MiB, or when switching from MiB to GiB:
  $$\text{displayValue} = \text{parseFloat}\left(\left(\frac{\text{rawMemory}}{1024}\right)\text{.toFixed(2)}\right)$$
• The display value is rounded to 2 decimal places to keep the UI clean, readable, and intuitive for users.
• Slider step dynamically adjusts:
  • In GiB mode: step is set to 0.01 (or smaller for sub-GiB offerings) with precision 2.
  • In MiB mode: step is set to 1 with integer precision 0.

2. Conversion from GiB to MiB (Backend Value Emission)

• CloudStack APIs and backend services expect memory allocations in integer MiB.
• When the user selects or inputs memory in GiB:
  $$\text{memoryInMiB} = \text{Math.round}(\text{displayValue} \times 1024)$$
• Exact Boundary Protection: If a compute offering has minimum/maximum memory constraints (minMemory / maxMemory), selecting the exact minimum or maximum bound in GiB directly maps to the exact integer minMemory or maxMemory in MiB to eliminate any potential off-by-one rounding discrepancies.

💬 Feedback Needed: Fractional GiB to Integer MiB Rounding

• Observation: Converting decimal GiB values to MiB often produces fractional values (e.g., 1.51 GiB × 1024 = 1546.24 MiB).
• Current Behavior: The UI rounds this to the nearest integer (1546 MiB), which is then emitted in the API payload and consumed by backend hypervisor managers.
• Reviewer Input: Looking for maintainer feedback on whether standard nearest-integer rounding (Math.round) is acceptable, or if we should apply ceiling (Math.ceil) to guarantee the VM always receives at least the requested GiB amount.

bandicam.2026-10-16.10-21-12-210.mp4